[PATCH v2 02/10] arm64/debug: Mask off all reserved bits from generated ESR values

[Dave Martin]

On Mon, Jul 13, 2015 at 03:14:40PM +0100, Mark Rutland wrote:
> On Mon, Jul 13, 2015 at 02:25:49PM +0100, Dave P Martin wrote:
> > There are only 16 comment bits in a BRK instruction, which
> > correspond to ESR bits 15:0.  Bits 24:16 of the ESR are RES0,
> > and might have weird meanings in the future.
> > 
> > This code inserts 16 bits of comment in the ESR value instead of
> > 20 (almost certainly a typo in the original code).
> 
> I'd guess that someone got confused with the instruction encoding where
> the immediate lives in bits 20:5, though the mask would be wrong anyway.
> 
> > 
> > Signed-off-by: Dave Martin <Dave.Martin at arm.com>
> 
> Looks sane to me.
> 
> Acked-by: Mark Rutland <mark.rutland at arm.com>

Cheers.

This was harmless up to now, anyway.  It will only bite if someone
passes x >= 0x10000, which they're not supposed to do.

---Dave

> 
> Mark.
> 
> > ---
> >  arch/arm64/include/asm/debug-monitors.h |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
> > index f3d2dbd..ab7d5a8 100644
> > --- a/arch/arm64/include/asm/debug-monitors.h
> > +++ b/arch/arm64/include/asm/debug-monitors.h
> > @@ -45,7 +45,7 @@
> >  /*
> >   * ESR values expected for dynamic and compile time BRK instruction
> >   */
> > -#define DBG_ESR_VAL_BRK(x)	(0xf2000000 | ((x) & 0xfffff))
> > +#define DBG_ESR_VAL_BRK(x)	(0xf2000000 | ((x) & 0xffff))
> >  
> >  /*
> >   * #imm16 values used for BRK instruction generation
> > -- 
> > 1.7.10.4
> > 
> 
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